Temperature dependent product distribution of electrochemical CO2 reduction on CoTPP/MWCNT composite

• Published in: Applied catalysis. B, Environmental Vol. 304; p. 120863
• Main Authors: Hossain, M.N., Prslja, P., Flox, C., Muthuswamy, N., Sainio, J., Kannan, A.M., Suominen, M., Lopez, N., Kallio, T.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-05-2022; Elsevier BV
• Subjects: Carbon dioxide; Catalysts; Chemical reduction; Co-based molecular catalyst; Cobalt; Electrochemical CO2 reduction; Electrochemistry; Electron transfer; Low temperature; Multi wall carbon nanotubes; Multiwalled carbon nanotube; Porphyrins; Protonation; Selectivity; Temperature dependence; Temperature selectivity dependence; Electrochemical CO2 reduction; Temperature selectivity dependence; Multiwalled carbon nanotube; Co-based molecular catalyst
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2021.120863

Electrochemical reduction of CO2 to valuable products on molecular catalysts draws attention due to their versatile structures allowing tuning of activity and selectivity. Here, we investigate temperature influence on CO2 conversion product selectivity over a Cobalt(II)-tetraphenyl porphyrin (CoTPP)/multiwalled carbon nanotube (MWCNT) composite in the range of 20–50 ℃. Faradaic efficiency of products changes with temperature and potential so that two-electron transfer product CO formation is enhanced at low potentials and temperatures while the competing hydrogen formation shows an opposite trend. Multi-electron transfer product methanol formation is more favorable at low temperatures and potentials whereas reverse applies for methane. Activity and selectivity are analyzed with DFT simulations identifying the key differences between the binding energies of CH2O and CHOH, the binding strength of CO, and the protonation of CHO intermediate. This novel experimental and theoretical understanding for CO2 reduction provides insight in the influence of the various conditions on the product distribution.
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•Temperature affects CO2 reduction product distribution on cobalt porphyrin (CoTPP).•By adjusting temperature CO to H2 ratio in syn-gas can be controlled.•CH3OH formation is observed at −0.6 VRHE at 20 ℃.•Higher temperature and potential facilitate CH4 formation.•Enhanced catalytic activity ascribed to CH-π interactions between CoTPP and support.